From genes to From genes to proteins. proteins.

(A dummies guide for Unit 3 Biology)(A dummies guide for Unit 3 Biology)

Source: http://library.thinkquest.org/C004535/protein_synthesis.html Ian Anderson – Saint Ignatius College, Geelong

Proteins.Proteins.

Proteins are macromolecules built up Proteins are macromolecules built up of amino acid monomers.of amino acid monomers.

They play a key role in living They play a key role in living organisms.organisms.

Each cell contains several hundred to Each cell contains several hundred to several thousand proteins.several thousand proteins.

They have specific structural and They have specific structural and functional roles (human proteome functional roles (human proteome estimated >100 000).estimated >100 000).

Functional diversity of Functional diversity of Proteins.Proteins.

StructuralStructuralForm the structural Form the structural components of tissues components of tissues and organsand organs

Collagen, keratinCollagen, keratin

RegulatoryRegulatory

Regulate cellular function Regulate cellular function (hormones, cell signaling)(hormones, cell signaling)

insulin, glucagon, insulin, glucagon, adrenalin, human growth adrenalin, human growth hormone, follicle hormone, follicle stimulating hormonestimulating hormone

ContractileContractileForm the contractile Form the contractile elements in muscle elements in muscle (skeletal, smooth, cardiac)(skeletal, smooth, cardiac)

myosin, actinmyosin, actin

ImmunologicalImmunological Combat invading Combat invading microbesmicrobes

antibodies such as antibodies such as gammaglobulingammaglobulin

TransportTransport Act as carrier moleculesAct as carrier molecules hemoglobin, myoglobinhemoglobin, myoglobin

CatalyticCatalytic Catalyze metabolic Catalyze metabolic reactions (enzymes)reactions (enzymes)

amylase, lipase, lactase, amylase, lipase, lactase, trypsintrypsin

Proteins.Proteins.

Everything a cell is or does depends Everything a cell is or does depends on the proteins it contains.on the proteins it contains.

Source: http://www.weberweb.net/animalcells.htm

Protein synthesis.Protein synthesis.

DNA carries the sets of instructions in DNA carries the sets of instructions in the chromosomes for every part of an the chromosomes for every part of an organism, including the production of organism, including the production of proteins.proteins.

Proteins however are manufactured on Proteins however are manufactured on ribosomes located in the cell cytoplasm.ribosomes located in the cell cytoplasm.

A method is therefore needed to transfer A method is therefore needed to transfer the information needed to build a protein the information needed to build a protein from the DNA to the ribosomes.from the DNA to the ribosomes.

Protein synthesis.Protein synthesis.

DNA cannot leave the nucleus, soDNA cannot leave the nucleus, so DNA stays in the nucleus and another DNA stays in the nucleus and another

molecule, acting as a messenger, molecule, acting as a messenger, carries the instructions from the DNA carries the instructions from the DNA to the ribosomes.to the ribosomes.

Proteins can now be manufactured by Proteins can now be manufactured by the ribosomes.the ribosomes.

This two stage process = protein This two stage process = protein synthesis.synthesis.

Protein synthesis.Protein synthesis.

Two stages of protein synthesisTwo stages of protein synthesis TranscriptionTranscription TranslationTranslation

Transcription.Transcription.

Relevant segment of DNA unwinds Relevant segment of DNA unwinds forming two single strands.forming two single strands.

Free floating nucleotides in nucleus Free floating nucleotides in nucleus bind to one strand following the base bind to one strand following the base pairing rulepairing rule adenine adenine uracil (not thymine) uracil (not thymine) cytosine cytosine guanine guanine

Complimentary copy of DNA, called Complimentary copy of DNA, called messenger RNA (mRNA), is formed.messenger RNA (mRNA), is formed.

Source: http://www.coolschool.ca/lor/BI12/unit6/U06L01.htm

Protein synthesis.Protein synthesis.

mRNA then leaves the nucleus and mRNA then leaves the nucleus and travels into cytoplasm and attaches travels into cytoplasm and attaches to a ribosome.to a ribosome.

The ‘message’ from the DNA can The ‘message’ from the DNA can now translated.now translated.

Translation.Translation.

Each sequence of three bases on the mRNA is Each sequence of three bases on the mRNA is called a codon (triplet code) and codes for a called a codon (triplet code) and codes for a particular amino acid.particular amino acid.

Amino acids are brought to the ribosomes by Amino acids are brought to the ribosomes by transfer RNA (tRNA) and linked in the transfer RNA (tRNA) and linked in the correct sequence to the mRNA according to correct sequence to the mRNA according to the triplet code.the triplet code.

Amino acids then join together to form a Amino acids then join together to form a polypeptide chain (the primary structure of a polypeptide chain (the primary structure of a protein).protein).

Order of amino acids defined by the original Order of amino acids defined by the original DNA instructions.DNA instructions.

Source: http://www.coolschool.ca/lor/BI12/unit6/U06L01.htm

Source: http://www.biochem.arizona.edu/classes/bioc471/pages/Lecture1/Lecture1.html